Production of leather



Patented June 4, 1929.

UNITED STATES PATENT OFFICE.

ROBERT HOWSON PICKARI), DOROTHY JORDAN LLOYD, AND ALBERT EDWARD CAUNCE, I 01 LONDON, ENGLAND.

PRODUCTION OF LEATHER.

No Drawing. Application filed August 22, 1925, Serial No. 51,8?3, and in Great Britain August 27, 1924.

This invention has reference to improvements in and relating to the production of leather.

It has been proposed to produce leather by first gradually removing the water from pelt, hide, or skin (all hereinafter included in the term pelt) by steeping the pelt for from 6 to 8 or more periods of 24 hours each in successively stronger baths of alcohol or .other solvent of water such as acetone. After each period of immersion the solvent is removed by pressure. After the pelt has been immersed in the last and strongest bath of the solvent itis dried at about 40 (1., and is then immersed in an alcoholic solution of tannin extract.

After the alcoholic tanning it may be advantageous to subject the tanned hide for a period of 24 hours to the action of an aqueous tanning solution.

This is not only a very lengthy and tedious process but the tanning is not completel effected owing to the stripping action 0; the alcohol.

In accordance with our invention the pelt is treated by steeping it at once in undiluted acetone (of full strength) the acetone being prefer ably free from its homologues, and maintaining it in the bath (or baths) of acetone until if a sample piece or cutting of the acetone saturated pelt is completely dried at approximately 135 F. (57 C.) it will immediately wet back i steeped inwater.

Of course, the actual time of immersion in the acetone will depend upon (a) the thickness and character of the pelt, and (b) the.

condition of the bath, that is to say whether or not it contains water.

If the pelt has not been maintained long enough in the acetone bath and therefore still contains a larger proportion of water than is desirable, a sample piece treatedwill not water bath, said specific gravity readily wet back in water.

In order to avoid making repeated tests as aforesaid it isdesirable that the pelt be maintained in the acetone until it is in equilibrium with a mixture of'acetoneand Water of specific gravity not greater than 0.810. That is to say, when the acetone and water contained in the fibres of the pelt is of the same specific gravity as the mixture of acetone and greater than 0.810. j

When the pelt has been treated as described,

the acetone in the pelt is at once removed byv being not evaporation which may be expedited, for example by air or inert gas heated to say 135 F. (57 C.) and/or vacuum, and the'hide now dried to the desired extent, as aforesaid, is, in

a condition admittingof its immediate im-.

mersion in the usual aqueous solutions of vegetable tan or chrome or a combination of these, or by a gaseous tanning agent, for instance formaldehyde. i

The important result of treating pelt as described is that the skin or hide is almost instantly penetrated by the aqueous tanning solution and thus a very considerable saving of time of at least 7 5% is obtained.

If desired the tanning need not be effected at once because the pelt, provided that the acetone treatment has been properly carried out, may be storeduntil it is required.

Should it be desired, the pelt, dried as de- I scribed, may be wet back preparatory to the tanning in the customary aqueous solution. In this case the speed of penetration is not so rapid as that obtained-when the pelt is immersed in dry condition as described above.

The pelt may besubjected to any usual preparatory treatment such as liming, batmg, etc., and if subjected to the treatment described may be wet back even if it has been stored for a very long period of time. Further, pelt as described may be heated up to wet back in water, evaporating oil the acetone from the pelt, hide, or skin,'and immersing it in an aqueous solution of tannin.

'until ifdried at a temperature of approximat-ely 135 F., (57 C.) it will immediately- 2. A processof producing leather which consists in immersing the pelt, hide, or skin, at once in ajbath of acetone of full strength until it is in equilibrium with a mixture of acetone and water of specific gravity not greater than 0.810, removing the acetone from the pelt, hide, or skin, and subjecting it to the action of an aqueous solution of tannin.

ROBERT HOWSON PICKARD. DOROTHY JORDAN LLOYD. ALBERT EDWARD CAUNCE. 

